Engine fuel pressure regulator



Nov. 27, 1956 c. KNUTH 2,771,868

ENGINE FUEL PRESSURE REGULATOR Filed Sept. 9, 1954 PIC-3.2. 3

i i 4 l6 Jrl l! l 9 7 A l II" I ll 1 H I (II INVENTOR. 27 CARL KNUTH Attorneys nited States Patent ENGINE FUEL PRESSURE REGULATOR Carl Knuth, Fond du Lac, Wis., assignor to Kiekhaefer Corporation, Cedarburg, Wis.

Application September 9, 1954, Serial No. 454,966

4 Claims. (Cl. 123-136) This invention relates to two-cycle engines utilizing crankcase induction and precompression of the fuel and air mixture and particularly to the liquid fuel supply system including a remote fuel tank having a line connecting the same with the crankcase whereby the pressure intermittently developed in the crankcase is utilized to pressurize the fuel tank for the delivery of the fuel to the engine.

According to the invention, the valve provided in the line to prevent the return of the fuel and air mixture from the tank to the crankcase because such pressure developed in the crankcase is intermittent, is subject to the pressure in the tank which causes the valve to open a limited degree so that only a lesser pressure is developed in the tank and whereby the valve serves to regulate the pressure in the tank. Such pressure regulation is desirable for safety considerations and because of the operating pressure limit of the carburetor. The pressure maintained by the regulator is preferably the minimum necessary for fuel delivery to the carburetor. The maximum pressure developed by crankcase compression is ordinarily not uniform at all engine speeds and the regulation of the pressure in the tank at a constant value further provides more consistent engine performance.

The drawings furnished herewith illustrate the best mode of carrying out the invention as presently contemplated as set forth hereinafter.

In the drawings:

Figure 1 is a view of a two cylinder two-cycle engine with parts broken away and sectioned and showing a fuel line connected to the carburetor;

Fig. 2 is an enlarged horizontal section of the engine shown in Figure 1 and is provided with the pressure regulator shown in section and connected to a fuel supply tank shown in section and having a delivery line to the carburetor of the engine; and

Fig. 3 is a fragmentary portion of the pressure regulator shown in Figure 2.

The engine 1 shown in the drawings includes the crankcase 2 carrying the crankshaft 3 and secured to the cylinder block 4. Each of the pistons 5 are connected by a rod 6 with the corresponding crank throw of a crankshaft 3 and are carried in the cylinders 7 of block 4 for alternate reciprocation. The bearing member 8 intermediate the crank throws of crankshaft 3 divides crankcase 2 into the upper and lower crank chambers 9 and 10 respectively associated with the lower ends of the corresponding cylinders 7. Bearing member 8 includes the induction passage 11 shown in dotted lines and which open into chambers 9 and 10. The carburetor 12 secured to crankcase 2 includes the mixing passage 13 which communicates through the crankcase with passage 11 in hearing member 8 for the delivery of air and carbureted fuel to chambers 9 and 10 in the operation of the engine.

In the operation of the engine, the upward stroke of each piston 5 compresses the fuel charge in the respective combustion chamber 15 above the piston. At the same ice time, the air and fuel mixture from carburetor passage 13 is drawn into the respective crank chamber. During the downward power stroke of the piston upon ignition of the compressed charge in the respective combustion chamber, the fuel and air mixture in the corresponding crank chamber is compressed for transfer through the commu nicating passage 16 which opens through the ports 17 above the piston into the cylinder. The exhaust ports 18 of each cylinder are controlled by the respective piston and are uncovered by the piston for the discharge of the exhaust gases through the ports slightly in advance of the similar opening of the corresponding ports 17 for the recharging of the cylinder with fuel and air mixture from the crank chamber as described.

The liquid fuel is supplied to carburetor 12 by the supply line 20 connecting the carburetor and the tank 21. The priming pump housing 22 forming a part of tank 21 carries the manually operable diaphragm 23 and the ballcheck valve 24 in the passage connecting the diaphragm chamber 25 and fuel supply line 20. The fuel is delivered to chamber 25 by the dip tube 26 extending from priming pump housing 22 to the lower portion of tank 21 and provided with the ball-check valve 27 at the lower end thereof. The supply of fuel from tank 21 to carburetor 12 is initially provided by manual operation of diaphragm 23 for starting engine 1. Thereafter the crankcase pressure within the crank chamber 9 having an opening communicating with the pressure regulator valve 28 and line 29 maintains a positive pressure within tank 21 which forces the fuel past valves 24 and 27 to carburetor 12. Valve 28 comprises the two housing members 31 and 32 and the thin metal diaphragm 33 marginally secured therebetween and separating the circular chambers 34 and 35 of the members, respectively.

Member 31 is secured to crankcase 2 by engine 1 with one end of the passage 36 formed in the member registering with an opening in the crankcase for communication with upper crank chamber 9. The other end of passage 36 opens into chamber 34 from the planiforrn valve seat 37 formed by the member and is disposed to be covered by the rubber disc 38 carried by diaphragm 33 within chamber 34.

The spring 39 in chamber 35 is disposed between the non-turning slide 40 carried by housing member 32 and the diaphragm oppositely of disc 38 to bias the disc against valve seat 37 and normally close passage 36.

In the operation of the engine 1, the intermittent pressure developed in crank chamber 9 operates against spring 39 to lift disc 38 within the limit of movement of diaphragm 33 and allow air and some gaseous fuel from the crank chamber into chamber 34 to pass through the pressure lines 29 connecting chamber 34 and tank 21.

Between the pressure periods developed in crank chamber 9, passage 36 is closed by disc 38 so that a positive pressure approaching the maximum pressure developed in chamber 9 is established within tank 21 soon after the engine is in operation.

According to the present invention, the diaphragm 33 is subject to the pressure within chamber 34 and tank 21 to prevent seating of disc 38 on valve seat 37 allowing some air and gaseous fuel in chamber 34 to re-enter crank chamber between the pressure periods referred to. 'The amount of pressure required to support diaphragm 33 against spring 39 as determined by the size of the diaphragm and capacity of the spring establishes generally the pressure maintained in tank 21. The screw 41 carried by member 32 and engaging slide 40 provides for adjustment of the compression of spring 39 and a corresponding adjustment of the regulated pressure in the tank.

As the pressure within the tank approaches a given maximum limit the pressure prevents seating of valve disc 38 so that the disc and valve seat 37 form a restr'icted orifice which allows limited flow of gases in both directions. The restricted flow which is allowed prevents the developmentof any greater. pressure within the tank because the same small amount-of gases passing into ,the tank during a single compression period of the crankcase is allowed to .return into the crankcase during the induction period which immediately follows. The amount of gases passing into the tank during any given compression period is relatively small by reason of the very brief period of time when a greater pressure in the crankcase actually obtains.

Conversely, the period during which the gases are or maybe allowed to return to the crankcase is much greater so that there is no possibility that a greater pressure in the .tank can be developed .in the tank. However, the amount of gases allowed to return is limited by the valve when the pressure in the tank reaches or is below a minimum. The disc 38 is then seated to prevent any return flow and the minimum pressure in the tank is thus established.

The regulated pressure in tank 21 is preferably the minimum pressure necessary to force the liquid fuel from tank 21 to the height of engine carburetor 12. The regulated pressure is quickly reached upon each starting of the engine when the effective operation of valve .28 in preventing return of air and gaseous fuel to the crank chamber is diminished by the pressure against diaphragm 33.

'Theioperation of valve 28 as a pressure regulator is not dependent on movement of the diaphragm at frequencies corresponding to higher engine speeds but will maintain a constant pressure within tank 21 regardless .of such .engine speed and allows the substantial construction of diaphragm 33 necessary to withstand the vibration of engine1. However, the valve 28 may also be directly associated with tank 21 with a line connecting passage 36 and crankchamber 9.

Various modes of carrying out the invention are contemplated as within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. In a fuel system for a high-speed engine employing crankcase precompression of the fuel and air mixture and having a remote fuel tank with a line for pressure effecting delivery of the fuel from the tank to the engine, a regulator valve for said pressure line comprising a rigid member and a flexible diaphragm secured to form a valve chamber connected with said line, said member having a passage from said chamber communicating with the engine crankcase, said diaphragm being yieldable to the pressure in said passage to periodically open the passage and allow gases from the crankcase into the valve chamher and to the tank, said diaphragm otherwise normally closing said passage to prevent the return flow of gases into said passage whereby the periodic pressure in the crankcase develops a constant pressure within the tank upon initial engine operation, and said diaphragm being further yieldable to said pressure in the chamber whereby a predetermined pressure within the tank and chamber prevents closing of the passage so that such pressure is thereupon maintained during continued engine operation.

2.1m an engine having a crankcase for the precompression of the fuel and air mixture, a fuel tank having a fuel delivery line connected to the engine, and a second line and a valve connecting the crankcase of the engine and the tank, said valve including means normally providing for the operation of the valve to allow the passage of gases from the crankcase to the tank under the pressure developed in the crankcase and to prevent return of the gases from the tank to .the crankcase whereby a pressure is developed in the tank which approaches the maximum pressure intermittently developed in the crankcase for the delivery of fuel to the engine through said other line, said means being further responsive to the pressure in the tank to allow gases from the tank approaching a given maximum pressure to return to the crankcase.

3. In an engine having a fuel tank for delivery of liquid fuel thereto and a crankcase for the precompression of the fuel and air mixture, a hollow valve body having a valve seat centrally therein and a passage communicating with :said engine crankcase and opening centrally of said valve seat, 'a yieldable diaphragm closing said chamber and seated against said valve seatto close said passage, a pressure line from said chamber to said tank, said diaphragm being yieldable to the pressure from the crankcase within said passage to allow the compressed fuel and air mixture into the chamber and to the tank, and adjustable biasing means to otherwise cause the diaphragm to close said passage whereby a pressure is developed in the tank to elfect delivery of the liquid fuel to the engine, and said diaphragm and biasing means being further yieldable to the pressure in said tank and chamber to open said passage when the pressure-within the tank and chamber reaches a predetermined value, said diaphragm being automatically operable to maintain the pressure within the tank at said value irrespective of but less than the maximum pressure intermittently developed in the crankcase.

4. In an engine having a crankcase for the precompression of the fuel and air mixture and .a fuel tank having a fuel delivery line connected to the engine, a valve comprising a member having a recess and a flexible diaphragm secured together to form a closed chamber, external and adjustable spring means biasing said diaphragm inwardly respecting said chamber, a valve seat in said chamber supporting said diaphragm against said spring means, a passage having an opening into said chamber defined by said valve seat and communicating with the crankcase of the engine, and means providing communication between said chamber and tank, said spring means normally providing for the operation of the diaphragm to allow the passage of gases from the crankcase to the tank under the pressure developed in the crankcase and to prevent return of the gases from the tank to the crankcase whereby a pressure is developed in the tank which approaches the pressure intermittently developed in the crankcase for the delivery of fuel to the'engine through said line, said spring means being further responsive to the pressure in the tank to allow gases from the tank approaching any given pressure to return to the crankcase, and thereby establish and maintain a given preselected pressure within the tank less than said maximum pressure.

. References Cited inthe fileof this patent UNITED STATES PATENTS 

